The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Internal combustion engines combust an air-fuel mixture and thereby produce a drive torque. To manage heat produced by the engine during combustion, a cooling system may be fluidly coupled to the engine. The cooling system may include a pump drivingly coupled to the engine that circulates coolant between the engine and a radiator. During operation, the coolant absorbs heat generated by the engine and dispels a portion of the absorbed heat to the surroundings. The cooling system may include a thermostat that inhibits the flow of coolant below a regulated temperature to allow the engine to heat up more quickly during cold starting and warm-up.
Operation of the engine may be regulated by a control module that receives various inputs from sensors of the engine and generates control signals that regulate actuators, such as a throttle, of the engine. The sensors may measure one or more operating conditions of the engine. Engine temperature is an important operating condition used in the control of the engine. The temperature of the engine may be estimated by determining a temperature of the coolant flowing though the engine. The coolant temperature is typically determined using a coolant temperature sensor in fluid communication with the coolant. The engine temperature is estimated based on the temperature of the coolant sensed by the coolant temperature sensor.
Engine diagnostic systems may monitor the operation of the engine, including the sensors and actuators included with the engine. When the diagnostic systems detect a problem with the coolant temperature sensor, a default coolant temperature may be used to regulate the engine instead of the measured temperature. For example, the engine may be regulated based on a coolant temperature estimate.